1. Field of the Invention
The present invention relates to a linear guide apparatus.
The present invention also relates to a linear guide apparatus provided with rollers as a rolling element.
2. Description of the Related Art
FIG. 22 shows an example of a related-art linear guide apparatus, which is provided with a guide rail 1 extending in an axial direction and a slider 2 mounted over the guide rail 1 so as to relatively move with respect thereto along the axial direction.
The guide rail 1 is provided with two (upper and lower) tracks of rolling element rolling grooves 3 axially extending on the respective side faces thereof, i.e., four tracks of rolling grooves in total. The slider 2 is separated into a slider main body 2A and end caps 5 in an axial motion direction, in such a manner that the end caps 5 are disposed on end portions of the slider main body 2A in the axial motion direction. The slider main body 2A includes leg portions 4 disposed widthwise over both sides of the guide rail 1, and a horizontal portion 7 connecting the leg portions 4. The horizontal portion 7 is mounted on an end face (an upper face of the guide rail 1 in the drawing) in a thicknesswise direction of the guide rail 1 (a direction perpendicular to both a longitudinal direction and a widthwise direction). The slider main body 2A is provided with rolling element rolling grooves 31 along an inner face of the respective leg portions 4 so as to oppose the rolling element rolling grooves 3 so that the rolling element rolling grooves 3, 31 constitute rolling passages for balls B.
A plurality of balls B serving as rolling elements is rollably disposed between the opposing rolling element rolling grooves 3 and 31, so that the slider 2 can relatively move with respect to the guide rail 1 in the axial direction via the rolling motion of the balls B.
Due to sliding motion of the slider 2, the balls B disposed between the guide rail 1 and the slider 2 roll toward an end portion of the slider 2; therefore the balls B are required to endlessly circulate in order that the slider 2 can continue the axial motion.
Accordingly, the slider main body 2A includes two (upper and lower) return passages 8 axially penetrating through the respective leg portions 4 of the slider main body 2A, i.e., 4 return passages in total, and each of end caps 5 includes semi-arc shaped direction reversal paths 6 so as to communicate with the rolling passages formed by the rolling element rolling grooves 3 and 31 and the return passages 8. The end caps 5 are fixed to front and rear end faces in the axial motion direction of the slider main body 2A with screws 12 or the like, thereby constituting endless circulation passages for the rolling elements with the rolling passages and the return passages 8 and the direction reversal paths 6. Furthermore, referring to FIG. 22 the reference numeral 10 denotes a tapped hole for fixing the end cap 5 to the end face of the slider main body 2A with screws, 11 a side seal, and 13 a greasing nipple disposed on a side or end face of the end cap 5.
It is essential, for ensuring smooth circulation of the balls B when fixing the end cap 5 to the end face of the slider main body 2A, to correctly align the direction reversal paths 6 of the end cap 5 with the respective rolling element rolling grooves 3 and 31, as well as with the return passages 8. Therefore, in related-art, a positioning groove 32 is simultaneously formed by grinding when forming the rolling element rolling grooves 31 on the slider main body 2A, along the axial direction parallelly between the upper and lower rolling element rolling grooves 31 as shown in FIG. 23 and FIG. 24. A projection 33 is formed on the end cap 5, which is to be engaged with the positioning groove 32 as shown in FIG. 25, so that the end cap 5 can be located in position by fitting the projection 33 into the positioning groove 32. (Japanese Published Unexamined Patent Application No. 2002-139035)
In the foregoing related-art linear guide apparatus, in case where an aperture deformation of the slider main body 2A because of a mounting operation of the slider 2 on the guide rail 1 and/or deformation due to heat treatment occur, generally the slider main body 2A, which has a C-shaped cross-section, is deformed in such a manner that the leg portions 4 open outwardly in the widthwise direction with respect to a center of rotation set at a center of the upper face of the slider main body 2A, and the aperture between the leg portions 4 becomes greater at a portion closer to end portions thereof.
Therefore, when engagement of the end cap 5 with the slider main body 2A is achieved at the positioning grooves 32 formed between the upper and lower rolling element rolling grooves 31 on the slider main body 2A as described above, since the lower rolling element rolling grooves 31 are provided below the positioning grooves 32 on the leg portions 4, deformation of a portion of the end cap 5 lower than the positioning grooves may not follow the deformation of the slider main body 2A. Therefore, positioning precision between the lower rolling element rolling grooves 31 on the slider main body 2A, which has made greater deformation, and the direction reversal paths 6 is degraded, thereby affecting circulation of the balls B.
In a linear guide apparatus provided with rollers as a rolling element, as disclosed in Japanese Published Unexamined Patent Application No. Hei. 5-209618, an overall length of a guide member 49 for guiding rollers 46 in an axial direction of a guide rail is made longer than an overall length of a slider main body 42, and end portions of the guide member 49 are inserted in engaging holes 48 formed on end caps 43a, 43b so that the end caps 43a, 43b are located in place with respect to the slider main body 42, as shown in FIG. 26.
In the linear guide apparatus disclosed in the above-mentioned document, since the position of the end caps 43a, 43b is determined via the guide member 49, as long as a size error of the guide member 49 or a positioning error in attaching the guide member 49 to the slider main body 42 is sufficiently small a problem will not arise. However, in a case where the size error or the positioning error becomes greater, the positioning precision of the end cap is deteriorated. Further, the structure disclosed in the above-mentioned document requires a bolt for fixing the guide member to the slider, which results in an increase in the number of components and assembly steps.